Pennycress Weed Control – Tips On Managing Pennycress

field pennycress
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By Bonnie L. Grant

Plants have been used for food, pest control, medicine, fibers, building material and other purposes since humans became bipedal. What was once an angel can now be considered a devil in many species. Pennycress plants are an ideal example.

Some of the more positive field pennycress facts reveal the plant has twice as much oil as soybeans, helps control some pests and reduces nitrogen run-off. And yet, they are branded a weed by many farmers and have an invasiveness rank of 42 out of 100 from the Alaska Natural Heritage Program. If the plant is not useful to you and is invading your land, learn how to control field pennycress by first identifying the plant and then choosing your treatment.

Field Pennycress Facts


Field pennycress (Thlaspi arvense) is native to Europe and has been transplanted to North America. In most states it is not a weed of concern but is has invasive potential in disturbed areas. While many of us view the plant as a nuisance farmers growing pennycress can effectively increase farm revenues by 25 – 30% by growing the herb as an overwinter crop. However the seeds can produce gastric problems when eaten by cattle and it has the potential to spread rampantly from its seed. A single plant can produce 20,000 seeds in its annual cycle.

Pennycress is a winter annual herb with simple to lobed leaves and tiny white flowers with four petals. It is a plant in the mustard family with a strong, unpleasant odor. The plant may be considered a weed in some areas of the United States but in the corn belt, it has potential as an off season crop.

Biodeisel companies have developed considerable interest in the plant and many agrofarms are planting it between corn and soybean crops. Once oils have been extracted from the plants, the seed meal remaining can be processed into plane fuel, livestock feed or protein additives for human consumption. These benefits may make farmers think twice about pennycress weed control.

Description of Pennycress Plants

Managing pennycress starts with recognizing the plant and its spread. The plant is 1 to 2 ½ inches tall. They start out as a rosette that spans 6 inches in diameter. The herbaceous leaves are oval to lance shaped, simple, alternate, 1 to 4 inches long and have distinct petioles.

If allowed to grow, the plant produces one or more rigid, ribbed stems. Flowers are produced at the ends of these stems in white racemes in mid spring to late summer. These develop into coin sized, flat pods with numerous tiny seeds. The root system has a deep taproot, making managing pennycress by hand pulling challenging.

How to Control Field Pennycress

Pulling the plants manually has success in small areas as long as you use a spade to get out all the roots. There are no known biological controls. Mowing or tilling before the plant produces seed is also a viable option but difficult to do in cropland, as seeds mature before crops have developed to harvest.

Pennycress weed control in agricultural situations is through the use of chemicals. Glyphosate, 2,4D, hexazinone, chlorsulfuron, metsulfuron, and picloram are the formulas listed in the Weed Control Book from the California Invasive Species Council as the most effective products. Multiple herbicide applications are necessary for consistent pennycress weed control.

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